1. Field of the Invention
The present invention relates to imaging apparatus (e.g. electrographic apparatus) and more specifically to such apparatus adapted for uniformly developing multi-image sections of web or strip type imaging media which move intermittently during imaging operations.
2. Description of the Prior Art
In electrographic apparatus wherein a plurality of electrostatic images are formed and liquid-developed sequentially along successive portions of a relatively long strip or web material (e.g. in roll-form), a problem is encountered when a break in imaging operations occurs before completion of the entire length of the strip of material. Such mid-strip stopping and restarting can occur, e.g., when a given batch of original documents is completed and more are not ready for recording, or when the operator desires to pause for other reasons. In general, the problem is presented because recorded images should be developed continuously for a period of predetermined duration in order to obtain high quality, and the pause of imaging operations leaves a section of imaged material at a standstill in the development station.
Various techniques have been attempted to obviate the problem. One solution is to cut the strip at its imaged/non-imaged interface when a pause occurs. The entire imaged portion can then be moved through the completion of its development in a continuous pass. The detractive features of this approach are that autothreading structure is required to recommence operations, and splicing is required to reconnect the strip sections for applications wherein its ultimate use is in roll form (e.g. a cassette of microimages).
Another technique that has been attempted in order to accommodate such start-stop development problems is displacing the development means from the strip (or vice versa) when strip-feed stops. In order to obtain complete development of all such displaced strip portions, which are at various positions along the development station when feeding stops, it is necessary, on restarting, to recommence development with those strip portions having their same relative position along the development station. However, a deterioration in image quality has been noted in this mode because a dried or partially dried layer of developer forms on the partially developed strip portions and causes development artifacts, such as fringe development, during subsequent development of those portions. A similar approach is to stop and restart the flow of liquid developer to the development zone in response to the strip-feed's stopping and restarting; however, the same kinds of quality deterioration have been noted with this approach.